This invention relates to rotary piston machines. It is concerned with an adaptation of the Stirling principle, with multi-sided rotary pistons operating in chambers with epitrochoidal lobes, the working fluid or vapour undergoing closed thermodynamic cyclic processes. The machine may operate as an engine or as a heat pump.
According to the present invention there is provided a fluid or vapour rotary piston machine including two variable-volume units, each unit having a rotary multi-lobed epitrochoidal chamber and a multi-sided rotary piston therein forming a plurality of invididual sub-chambers by its co-operation with the periphery of the associated chamber, the number (n+1) of piston sides being greater by one than the number (n) of epitroichoid arcs, wherein the two chambers are constrained to rotate at a first common speed about a first effective common axis while the two pistons are constrained to rotate at a second common speed about a second effective common axis, the ratio of first to second common speeds being n+1:n, wherein each chamber has a plurality (n) of dual-function ports enabling connection between the chambers via ducts, and wherein said ducts each contain a regenerator, enabling one variable-volume unit to perform intake, expansion and exhaust, while the other unit performs intake, compression and exhaust, as a result of the relative rotation and port positions.
Preferably, the chambers will be co-axial, as will be the rotors. That simplifies construction. But they could, in theory, be on different axes but coupled to rotate in liaison. The term xe2x80x9ceffectivexe2x80x9d is intended to cover this alternative.
Heating means may be provided for the variable-volume unit which performs the expansion processes, as shown schematically in FIG. 7, and there could be further heating means between each said regenerator and the variable-volume unit which performs the expansion processes.
Cooling means may also be provided for the variable-volume unit which performs the compression processes, as shown schematically in FIG. 7, and there could be further cooling means between each said regenerator and the variable-volume unit which performs the compression processes.
In the preferred form n=2, so that there are three sided pistons operating in double-lobed chambers.
The expansion unit which may, but not necessarily, be heated, will have its ports disposed in such a way that the chambers formed therein are increasing in volume generally when not in communication with a port and decreasing in volume generally when said chambers are in communication with a port. The other, compression unit which may, but not necessarily, be cooled, will have its ports disposed in such a way that the chambers formed therein are decreasing in volume generally when not in communication with a port, and increasing in volume generally when said chambers are in communication with a port. Work processes thus occur in chambers isolated from port openings, while the transfer of working fluid or vapour occurs between a pair of chambers each in communication with ports opening to a common duct. If high-grade heat transfer is accomplished to the working fluid or vapour flowing to, from or contained within, the expansion unit, while low-grade heat transfer is accomplished from the working fluid or vapour flowing to, from, or contained within, the compression unit, the machine behaves as an engine, with mechanical work output. If mechanical work is applied to the rotating components, but low-grade heat transfer is accomplished to the region of the expansion unit while high-grade heat transfer occurs from the region of the compression unit, the machine behaves as a heat pump or refrigerating machine.